IDO1 and neoplasm: Many researchers have analyzed its cellular composition (CD4, CD8, Tregs, NK cells, TAMs, etc.)and secretion of molecules involved in tumor growth (e.g., cytokines, chemokines, cytokine receptors) and immunosuppression (e.g., PD-1, PD-L1, IDO, MHC-I, MHC-II).